Motor-controller.



T. E. BARNUM. MOTOR CONTROLLER.

APPLICATION FILED SBPT.9.1911.

1,1 1 3,289. Patented 001. 13, 1914.

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UNITED STATES" PATENT OFFICE.

THOMAS E. BARNUM, OE MILWAUKEE, WISCONSIN, ASSIGNOR TO THE CUTLER- HAMMER MFG. 00., OF MILWAUKEE, WISCONSIN, A CORPORATION OF WIS- CONSIN. I

MOTOR-CONTROLLER.

1,113,285 p mcaaoror ream m 'Patented Oct. 13, 1914.

Application filed September 9, 1911. Serial No. 648,532.

To all whom it may concern: I

Be it known that I, THOMAS E. BAnNUM, a citizen of the United States, residing at ltlilwa ikee, in the county of Milwaukee and" Stateof Wisconsin, have invented new and useful Improvements in Motor-Controllers, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawing, forming a part of this specification.

My invention relates to improvements in the method of and means for controlling electric motors.

In practice I have found, especially with the squirrel cage, A. C. motors that the reduction of voltage desired for starting so reduces the starting torque that the acceleration of 'the motor is very slow until it has, reached approximately half speed. I have also found in practice that due to the peculiar characteristics of such motors the reduction of current taken by the motor is also slow and is only reduced to a small degree upon the motor attaining half speed. Where such conditions are met with the ordinary means used for controlling such motors falls far short of giving ideal starting conditions. According to my invention I propose Where such conditions prevail to maintain the impressed voltage at a minimum until the motor reaches approximately one-half of any desired proportion of its normal speed, thereby insuring full protection during this period of slow acceleration. I then propose to remove a certain proportion of the voltage reducing means and to continue the acceleration of the motor without further change until the same has reached approximately' three quarters or any other desired proportion of its full speed whereup I remove another section of the voltagereducing means. Thereafter the remainder of the voltage reducing means may be more quickly removed from circuit either gradually or in one step as desired. Y

Various means may be employed for carrying out the foregoing method of acceleration. In practice, however, I prefer to employ a device having a controlling element which has a comparatively wide range of movement over a series of contacts and to so connect the voltage reducing means to said. contacs as to necessitate movement ofrthe cont-re. ng member to such an extent prior to the removal of successive sections of the voltage reducing means to enable the motor to attain the desired proportion of its full speed. 1

While my invention is particularly applicable to the control of squirrel cage motors it is also applicable to other types of motors including direct current motors and especially shunt wound direct current motors.

In order to more clearly and fully disclose the nature and characteristic features of my invention I shall describe the embodiments thereof, diagrammatically illustrated in the accompanying drawing. It should be understood, however, that.my invention is not limited to the specific embodiments thereof illustrated or to these specific applications thereof.

In the accompanying drawing, Figure 1 is a diagrammatic view of a controller for squirrel cage motors, and Fig; 2 is a diagrannnatic view of a controller for a shunt wound D. motor.

Referring first to the A. C. controller I have shown the same used for controlling resistances R and R connected in circuit with the primary winding P of a threephase A. C. squirrel cage motor. The controller comprises a pivoted arm 1 formed in three sections the sections 2 and 3 thereof. being insulated from the section 1- and accordingly from each other. The arm is pro vidcd with a suitable operating handle 4. The section 2 carries contact brushes 5 and 6 electrically connected through said section The brush 5 is adapted to engage and sweep over a series of contact buttons 7 while the brush 6 is adapted to engage and move over a contact segment 8. The section 3 of the arm is also provided with two electrically conne'cted contactbrushes 9 and 10, which, like the brushes 5 and 6 are electrically connected. The brush 10 is adapted to engage with and sweep over a series of contact buttons 11 while the brush 9 is adapted to engage and move 'over a segment removing any of the resistance R and must then be moved slightly over one-half the rem nlng distance before further removing any of the resistance. The first four contact buttons are electrically connected; the next three buttons are'electrically connected and the next two buttons are electrically conn ected. The resistance R is connected in a similar manner to the buttons 11 and the buttons 11 are also connected in a similar manner, the connections of the buttons and of the resistance with the buttons being reversed on account of the sections 2 and 3 of the controlling arm being moved in opposite direction. With such an arrangement it will be seen that the arm must be moved approximately one-half of its full movement before removing any of the resistances and approximately three quarters of its full movement before further removing any of the resistances.

The extreme right hand button of the series of buttons 7 is connected by a conductor 14 with one terminal of the primary winding while the extreme left hand button on the seriesof buttons 11 is connected by conductor 15 with a second terminal of the motor. The third terminal of the motor is connected by conductor 16 directly to one line of the supply circuit 17, 18, 19. The other two lines of the supply circuit are connected to the segments 8 and 12.

With the controller in the position illustrated the circuit of the primary winding is open. To close this circuit the controller arm should be moved in a clockwise direction to cause the section 2 thereof to bridge and electrically connect the segment 8 and the buttons 7 and the section 3 to bridge and electrically connect the segment 12 and contact but-tons 11. Continued movement of the controller arm in a clockwise direction will, of course, remove the resistances to ac-' celerate the motor.

Assuming that the range of movement of the controller arm is sufiicient to enable the motor to attain full speed before-said arm reaches the limit of its movement and that, as is customary in practice, the arm is moved at a slower speed during theinitial part of its movement than during the latter part of its movement, it will be seen that the mo a device including a controller arm 20 movable over a series of contact buttons 21. The contact buttons 21 are connected to a resistance R connected in series with the motor armature. The buttons 21 are connected together in a manner similar to that shown in Fig. 1 and the resistance R is connected to the buttons also ina similar manner to that shown in Fig. 1. With the arm 20 in the position illustrated, the armature circuit is opened. The shunt field winding is permanently connected across the supply lines 22 and 23. To start the motor the arm 20 should be moved in a clockwise direction thereby closing the armature circuit and thereafter removing the resistance R in steps, the first step being removed upon approximately one-half ofthe movement of the arm 20, the second step upon approximately three quarters of the movement of said arm and the third step upon full movement of the arm. This results as in the previous device in maintaining the same voltage conditions until the motor attains approximately one-half of its full speed. The voltage is then increased but is not further altered until the motor attains approximately three quarters of the full speed and then after a predetermined movement of the arm, full voltage is supplied.

What I claim as new and desire to secure by Letters Patent is as follows 1. A motor starting device provided with an element movable at a uniform rate of speed to increase the power supplied to the motor at intervals gradually diminishing in duration.

2. Inamotor starter, in combination, voltage reducing means and controlling means therefor including an element movable at a uniform rate'of speed to maintain all of said voltage reducing means in circuit until the motor has reached approximately one-half of its normal speed and thereafter Vary said voltage reducing means at intervals 'gradually diminishing in duration.

3. In a device for starting electric motors in combination; voltage reducing means and a controlling element therefor, movable in steps of varying lengths to remove said voltage reducing means in a corresponding number of sections.

4. In a controller for starting electric motors, in combination. voltage reducing means and a controlling element movable in steps successively decreasing in length to remove said .voltage reducing means in a corresponding number of sections.

5: In acontroller for starting electric motors, in combination, voltage reducing means, a movable controlling element and a series of cooperating contacts therefor, controlling said voltage reducing means and connections between said, voltage reducing means and said contacts necessitating varying degrees of movement of said controlling element to remove successive sections of sai voltage reducing means.

6. In a controller for starting electric motors, in combination, voltage reducin means, a series of contacts connected to sai voltage reducing means to divide the same into a plurality of steps and a controlling member movable over said contacts to remove said voltage reducing means from circuit, the removal of said voltage reducing means necessitating movement of said con- In witness whereof, I have hereuntosub- 15 scribed my name in the presence of two witnesses.

THOMAS ,E. BARNUM.

Witnesses:

E. H. ROCKWELL, FRANK H. HUBBARD.

Copies of this patent may be obtained for five cents each, by addressing the "Commissioner of Patents,

Washington, D. 0. 

